#include<stdio.h>
int main(void){
	int s,grade;
	scanf("%d",&s);
	grade=s/10;
	switch(grade){
		case 10:
		case 9:
		printf("A\n");
		break;
		case 8:
		printf("B\n");
		break;
		case 7:
		printf("c\n");
		break;
		case 6:
		printf("D\n");
		break;
		default:
		printf("E\n");
		break;
			
	}
	return 0;
} 
